Double-ended electric incandescent lamp



Jan. 20, 1948. P. o. CARTUN DOUBLE-ENDED ELECTRIC INCANDESCENT LAIP Filed Feb. 28. 1947 n 1 Q r n E F m e T O ,n

Patented Jan. 20, 1948 UNITEDI- STATES 2,434,757 DOUBLE-ENDED ELECTRIC INCANDESCENT Paul 0. Cartun, Cleveland Heights, Ohio, minor to General Electric Company, a corporation of New York Application February 28, 1947, Serial No. 731,506 6 Claims. (01. 176-29) My invention relates to electric incandescent lamps and similar devices, and more particularly to a support arrangement for the mounts of such lamps. The invention is of particular utility in connection with electric incandescent lamps of the double-ended tubular type having a base at each end and a filament extending longitudinally of the lamp, such as shown and described in U. S. Patents 2,032,791, P. O. Cartun, and 2,158,849, H. D. Blake, assigned to the assignee of the present invention.

Lamps of the above mentioned double-ended tubular type are in general use at present, such lamps being commonly known as Lumlline" lamps. As manufactured at present, these lamps comprise a tubular glass envelope having metal end caps or bases sealed to the opposite ends thereof and an elongated mount supported within the envelope between the metal end caps. The mount comprises an elongated filament extending longitudinally of the envelope and supported by an elongated stay member which is resiliently compressible longitudinally between the end caps and which is provided at its opposite ends with terminal wires or end conductors which are electrically connected to the ends of the filament. The said terminal conductors of the stay memher are formed with loop portions which bear against the end caps and encircle inward bosses n the said caps.

With lamps of the above described construction, the mounts are free to rotate or turn within. the envelope about the longitudinal axis thereof, the only restraint to such rotation being the frictional resistance which is exerted on the terminal conductor loops by the end cap, by reason of the pressure engagement therebetween. As a result, the mounts of such lamps, particularly in those applications where the lamps are subject to frequent shocks and vibration, actually, do undergo a certain amount of rotation within the envelope. Obviously, the prevention of such mount rotation is to be desired, especially in those cases where the envelope is provided with a light-reflecting coating around a portion of its circular extent. In such cases it is preferable to maintain the mount in fixed relation to the reflector, with the stay member located within the reflector, in order to prevent the stay member from casting a shadow or producing a dark spot in the projected beam of light.

It is an object of my invention, therefore, to provide an electric lamp of the character described having a mount which will not be subject to rotation within the lamp envelope.

Another object of my invention is to provide an electric incandescent lamp of the character described having means for positively locking the lamp mount against rotation within the lamp envelope.

Still another object of my invention is to provide an electric incandescent lamp of the character described having a reflective coating on a portion of the envelope wall and a mount structure locked in predetermined relation to the said reflector.

Further objects and advantages or my invention will appear from the following detailed description of a species thereof and from the accompanying drawing in which;

Fig. 1 is an elevation, partly in section, of an electric incandescent lamp comprising my invention; Fig. 2 is a transverse section on the line 2-2 of Fig. 1; and Fig. 3 is a longitudinal section,

2 on the line 3-3 of Fig. 2, of the end of the lamp shown Fig. 2.

Referring to the drawing, the lamp there shown is of the double-ended tubular type shown in the above mentioned U. S. Patents 2,032,791 and 2,158,849, and comprises an elongated sealed envclope 5 consisting of a tubular glass bulb 2 having disc-shaped metal end caps or.bases 3 fusionsealed to its opposite ends to form end walls for the envelope and contact terminals for the lamp.

to The said end caps or discs 3 are preferably made of a metal or alloy which has a'coefficient of expansion approximately the same as that of the 'glass of which the tube 2 is made and which seals readily thereto .by fusion. For a soft glass tube 2, the end capst, ii are preferably made of an.

iron alloy containing about 25 to 30 per cent chromium. The end caps 3, 4 are preferably concave or dish-shaped so that they may be made of thin material while retaining adequate strength, and they are provided with centrally located bosses 5, 6 which project axially inward of the envelope l The particular lamp illustrated is provided with a reflector which may be in the form of a reflecting coating 1 on the glass tube 2 extending substantially the full length thereof and around a portion (approximately one-half in the particular case shown) of thecircular extent of the glass tube. The reflecting coating 1 may be of aluminum, silver or other suitable reflect- 5o ing material. Instead of the reflector .l, the glass l is exhausted through an aperture 24 at the center of the end cap 3, the said aperture being sealed by a mass of glass 25 which constitutes thecomprising a composite sta member 9 and an elongated filament l supported thereby. The filament supporting structure or stay member 9 comprises an elongated straight center section II extending longitudinally of the tube 2 adjacent the wall thereof and-provided at its opposite.

ends .with terminal wire or end conductor extensions l2, I3. The center section II of the stay member 9 is preferably-in the form of a channelshaped member of a suitable material, for instance a stainless steel such as that commercially known as Allegheny metal. The terminal wire I2 is electrically connected, as by welding, to one end of the channel member H while the other terminal wire I3 is secured to the other end of the "said channel member H by a short length of glass rod M which is fused to the said parts and.

I3, respectively. The filament i0 is supported at intermediate points along its length by one or more support wires ll extending from the channel member H at spaced points therealong, the said support wires being secured to and insulated from the channel member by means of small glass.

beads 18 fused to the said parts.

As shown, the terminal wires or end conductors l2, l3 extend from the opposite ends of the channel member I l at a slight angle relative thereto, and their free or outer ends are bent to extend transversely of the channel member ii and are formed into loops 89 which encircle the bosses 5, 6 on the respectively adjacent end caps to thereby position the lamp mount 8 within the envelope l with the filament ill extending more or less axially of the said envelope. The loop E9 on one or both terminal Wires l2, I3 is initially formed with a Slight pitch or spiral shape, 1. e., it is formed as a coil of less than one full turn, for the purpose of making the stay member 9 resiliently compressible to' a slight extent longitudinally thereof. During the manufacture of the lamp, the

spiralshaped loop or loops l9 more or lessfiatten out as the stay member 9 is compressed between the opposite end caps 3, Q, the loops it thus resiliently bearing against the concave inner side of the end caps and so making good electrical contact therewith.

In accordance with the invention, means it are provided for preventing rotation or turning of the mount ii within the envelope I about the axis of the latter. For this purpose, an anchor member 22, such as a short length of Dumet wire, which will fuse and seal to the glass of the envelope l, is welded to the end loop i9 on end con ductor l2, preferably adjacent the 'free end thereof, so as to extend more or less radially outward from the said loop IS. The free end of the anchor wire 22 extends into and is embedded in the glass seal 23 between the adjacent end cap t and the glass tube 2. thus anchoring the mount t against rotation within the envelope.

As shown. the mount 8 is anchored by the anchor wire 22 in a definite rotative position within the envelope l with the stay member 8 positioned contiguous to and within the confines of the refiector "I on the envelope, preferably midway between the opposite side edges of the said reflector. In this way, the stay member 8 is shielded by the reflector l and so does not interfere with the passage of the light out through the clear or light transmitting portion of the envelope so as to cast undesirable shadows.

What I claim as new and desire to secure by Letters Patent of the United States'is:

1. An electric lamp comprising an envelope including a tubular glass bulb provided with lightmodifying means extending substantially the full length thereof and around a portion of its circular extent and having end caps sealed to and enclosing its opposite ends. each of said end caps having a boss projecting inwardly of the envelope, a mount within said envelope comprising an elongated filament extending longitudinally of the envelope and a filament-supporting elongated with a loop portion encircling the boss on the respectively adjacent end cap, and means on said stay member engaging said envelope to lock the said mount in a predetermined rotative position within said envelope with the stay member thereof disposed within the confines of the said lightmodifying means so as to be shielded thereby.

2. An electric lamp as claimed in claim 1 wherein the light-modifying means comprises a reflecting coating on the glass bulb.

3. An electric lamp as claimed in claim 1 wherein the means for locking the mount against rotation comprises an anchor member secured to the stay member and fused to the glass bulb.

4. An electric lamp as claimed in claim 1 wherein the loop on one of said end conductors is provided with an extension fused into the glass seal between the adjacent end cap and the glass bulb.

5. An electric lamp as claimed in claim 1 wherein the means for locking the mount against till free end and extending radially outward from said loop. and fused into the glass seal between the adjacent end cap and the glass bulb.

PAUL O. CARTUN. 

